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Viessmann DHW Temp


We have a Vitotronic 200 model KW2 controller on our Viessmann oil boiler, installed by prior owner in 2003. It runs a Crown DHW tank. The other day, we had no hot water. The DHW temperature was reading 262 F. Obviously, bad DHW sensor. No issues with any of it up to this point.

Tech came out and installed a new DHW sensor and left. No adjustments were made. Now, the water isn't nearly as hot as it used to be. I had the DHW temp set to around 120 before any of this happened. Now, even if I crank it up to 135, it's noticeably cooler coming out of the shower.

Is there something that I can adjust, or do I need another new sensor?


  • mikeinrimikeinri Member Posts: 2
    Never Mind...

    Tech came back today, the new sensor is working correctly, confirmed with a digital thermometer at the faucets (matched Vitotronic display within 1.5 degrees).

    He tells me that the most likely issue with cooler shower temperature is a mixing valve problem (need to clean/rebuild Temptrol valve on shower).

    Is it really possible for the old sensor to have been reading low all these years, causing the water temperature to be higher than it is now at the same setpoint (120 F)?

    Seems very odd that all of this is a coincidence, but at least he didn't charge for the follow up visit.
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